The present invention relates to a reciprocating piston type of internal combustion engine, and particularly to such an engine having a balancing mechanism for preventing vibration of the engine.
Internal combustion engines have recently been made smaller and more lightweight by increasing the rotational speed of the crankshaft, thereby, of course, increasing the frequency of reciprocation of the piston and other parts. This new design also increases the forces and moments of inertia of the parts, causing disadvantageous vibrations of the engine.
An attempt to counterbalance the forces and prevent such vibrations is shown in Harkness U.S. Pat. No. 3,457,804, wherein a counterbalance is supported by arms on eccentric journals fastened to the crankshaft, the counterbalance being on the side of the crankshaft which is opposite to the cylinder. A link is pivotally connected to the counterbalance and to a wall of the crankcase. As the crankshaft rotates, the counterbalance moves in an arc having its center at the pivotal connection to the crankcase and therefore the counterbalance cannot move completely axially of the cylinder. This arcuate motion produces forces in the counterbalance which exceed the mass of the reciprocating parts such as the piston. As a result, the inertia forces of the reciprocating parts are not balanced, and the vibrations along and transverse to the cylinder axis are not effectively reduced.
It is a general object of this invention to provide an improved balancing mechanism for such an engine, including a counterbalance which moves axially of the cylinder in order to balance the inertia forces of the piston and other reciprocating parts of the engine.